According to the state of the art, a data stream, such as an audio and/or video stream, transmitted through a packet transport network, is associated with one or several error correction streams, for example FEC (Forward Error Correction). According to the state of the art, a data stream receiver is capable of using one or several error correction streams to correct errors which can be identified during the reception of the data stream.
An error correction stream associated with a data stream includes redundancy data. This data allows a receiver to correct errors at reception, for example packets or data lost or received with errors. A data stream receiver, which receives one or several associated error correction streams, can then correct a number of errors in the data stream received by using an operation comprising the use of packets correctly received from the data stream and the use of redundancy data.
A data stream correction by using one or several associated error correction streams allows recovery of up to, for example, 20% of packet loss in the data stream without affecting the rendering property of a video stream, according to the encoding parameters of the error correction stream at transmitter level.
This technique thus allows considerable improvement of the rendering quality of a video stream in the case of packet loss or in the case of reception of erroneous packets, for receivers which are subjected to these types of disturbances.
However, the generation of an error correction stream by a transmitter, as well as the use of one or several correction streams by a receiver have a non-negligible impact for the transmitter and for the receiver, in terms of CPU (Central Processing Unit) load, of transmission delay, and/or of decoding delay, resulting in a display delay during a channel change or “zapping”, and/or also in terms of occupation of the transport network or of use of the network bandwidth, which can limit the number of data streams which can be transmitted on a packet transport network.
The standard for the transmission of video and/or audio services “DVB-IP” is available at the ETSI under the number ETSI TS 102 034 whose title is “Digital Video Broadcasting (DVB); Transport of MPEG-2 TS based DVB services over IP based networks (DVB-IPI)” is an example of the use of error correction streams into a packet transport network.
According to the prior art, the use of one or several error correction streams associated with a data stream is predetermined for a set of receivers, even if some receivers encounter few errors, which penalises the transmitter as well as the receivers relating to the terms described above (CPU load, zapping time, occupation of the broadcast network). The data stream and the error correction stream(s) are often transmitted on multicast broadcast addresses, in order to make these streams available for a high number of receivers.
So, the state of the art has the disadvantage of non-optimized management, of error correction stream(s) associated with a data stream, through a packet transport network.